The objective of this project is to evaluate the capabilities of various tissue lipases and esterases as early mediators in the interactions of animals with xenobiotics containing ester linkages. These enzymes are also used as models in studies of protein-ligand interactions. A new procedure for the purification of nonspecific lipase has been developed, permitting its preparation on a larger scale than was previously possible. Its interaction with cofactors and substrates will be studied by circular dichroism and fluorescence spectroscopy.